Are you still on Windows Server 2003 and want to migrate to Server 2012?  This article outlines how the Server 2012 migration tools can make this process as simple as possible, and better yet, the tools come with Server 2012. Read more here at Matt Hester's blog:

http://blogs.technet.com/b/matthewms/archive/2013/02/13/migration-and-deployment-installing-the-migration-tools-part-8-of-19.aspx